From 2d5eaadb75cbfa77d3e2e84d037b8133ba62f46d Mon Sep 17 00:00:00 2001
From: Grzegorz Piwowarek <gpiwowarek@gmail.com>
Date: Mon, 16 Sep 2024 09:11:11 +0200
Subject: [PATCH] Rewrite max parallelism tests (#941)

---
 .../pivovarit/collectors/FunctionalTest.java  | 20 -----------------
 .../collectors/test/BasicParallelismTest.java | 22 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/test/java/com/pivovarit/collectors/FunctionalTest.java b/src/test/java/com/pivovarit/collectors/FunctionalTest.java
index a9ab4474..dee31364 100644
--- a/src/test/java/com/pivovarit/collectors/FunctionalTest.java
+++ b/src/test/java/com/pivovarit/collectors/FunctionalTest.java
@@ -174,7 +174,6 @@ private static <R extends Collection<Integer>> Stream<DynamicTest> tests(Collect
           shouldInterruptOnException(collector, name)
         );
 
-        tests = limitedParallelism ? of(shouldRespectParallelism(collector, name)) : tests;
         tests = limitedParallelism ? of(shouldRejectInvalidParallelism(collector, name)) : tests;
 
         return tests;
@@ -190,7 +189,6 @@ private static <R extends Collection<Integer>> Stream<DynamicTest> virtualThread
     private static <R extends Collection<Integer>> Stream<DynamicTest> streamingTests(CollectorSupplier<Function<Integer, Integer>, Executor, Integer, Collector<Integer, ?, CompletableFuture<R>>> collector, String name) {
         return of(
           shouldStartConsumingImmediately(collector, name),
-          shouldRespectParallelism(collector, name),
           shouldPushElementsToStreamAsSoonAsPossible(collector, name),
           shouldShortCircuitOnException(collector, name),
           shouldRejectInvalidParallelism(collector, name)
@@ -209,24 +207,6 @@ private static <R extends Collection<Integer>> Stream<DynamicTest> batchStreamin
           of(shouldProcessOnNThreadsETParallelism(collector, name)));
     }
 
-    private static <R extends Collection<Integer>> DynamicTest shouldRespectParallelism(CollectorSupplier<Function<Integer, Integer>, Executor, Integer, Collector<Integer, ?, CompletableFuture<R>>> collector, String name) {
-        return dynamicTest(format("%s: should respect parallelism", name), () -> {
-            int parallelism = 2;
-            int delayMillis = 50;
-            withExecutor(e -> {
-                LocalTime before = LocalTime.now();
-                Stream.generate(() -> 42)
-                  .limit(4)
-                  .collect(collector.apply(i -> returnWithDelay(i, ofMillis(delayMillis)), e, parallelism))
-                  .join();
-
-                LocalTime after = LocalTime.now();
-                assertThat(Duration.between(before, after))
-                  .isGreaterThanOrEqualTo(ofMillis(delayMillis * parallelism));
-            });
-        });
-    }
-
     private static <R extends Collection<Integer>> DynamicTest shouldPushElementsToStreamAsSoonAsPossible(CollectorSupplier<Function<Integer, Integer>, Executor, Integer, Collector<Integer, ?, CompletableFuture<R>>> collector, String name) {
         return dynamicTest(format("%s: should push elements as soon as possible ", name), () -> {
             int parallelism = 2;
diff --git a/src/test/java/com/pivovarit/collectors/test/BasicParallelismTest.java b/src/test/java/com/pivovarit/collectors/test/BasicParallelismTest.java
index c8ec9dc4..a3ef1d0d 100644
--- a/src/test/java/com/pivovarit/collectors/test/BasicParallelismTest.java
+++ b/src/test/java/com/pivovarit/collectors/test/BasicParallelismTest.java
@@ -1,14 +1,18 @@
 package com.pivovarit.collectors.test;
 
 import com.pivovarit.collectors.ParallelCollectors;
+import com.pivovarit.collectors.TestUtils;
+import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.TestFactory;
 
+import java.time.Duration;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collector;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
@@ -22,7 +26,8 @@ class BasicParallelismTest {
 
     private static Stream<CollectorDefinition<Integer, Integer>> allBounded() {
         return Stream.of(
-          collector("parallel(e, p)", (f, p) -> collectingAndThen(ParallelCollectors.parallel(f, e(), p), c -> c.join().toList())),
+          collector("parallel(e, p)", (f, p) -> collectingAndThen(ParallelCollectors.parallel(f, e(), p), c -> c.join()
+            .toList())),
           collector("parallel(toList(), e, p)", (f, p) -> collectingAndThen(ParallelCollectors.parallel(f, toList(), e(), p), CompletableFuture::join)),
           collector("parallel(toList(), e, p) [batching]", (f, p) -> collectingAndThen(ParallelCollectors.Batching.parallel(f, toList(), e(), p), CompletableFuture::join)),
           collector("parallelToStream(e, p)", (f, p) -> collectingAndThen(ParallelCollectors.parallelToStream(f, e(), p), Stream::toList)),
@@ -52,6 +57,15 @@ Stream<DynamicTest> shouldProcessAllElementsWithMaxParallelism() {
             })));
     }
 
+    @TestFactory
+    Stream<DynamicTest> shouldRespectMaxParallelism() {
+        return allBounded()
+          .map(c -> DynamicTest.dynamicTest(c.name(), () -> {
+              var duration = timed(() -> IntStream.range(0, 10).boxed().collect(c.factory().collector(i -> TestUtils.returnWithDelay(i, Duration.ofMillis(100)), 2)));
+              assertThat(duration).isCloseTo(Duration.ofMillis(500), Duration.ofMillis(100));
+          }));
+    }
+
     protected record CollectorDefinition<T, R>(String name, CollectorFactory<T, R> factory) {
         static <T, R> CollectorDefinition<T, R> collector(String name, CollectorFactory<T, R> collector) {
             return new CollectorDefinition<>(name, collector);
@@ -66,4 +80,10 @@ private interface CollectorFactory<T, R> {
     private static Executor e() {
         return Executors.newCachedThreadPool();
     }
+
+    private static Duration timed(Supplier<?> action) {
+        long start = System.currentTimeMillis();
+        var result = action.get();
+        return Duration.ofMillis(System.currentTimeMillis() - start);
+    }
 }